I have the TT locking bracket for my eTrex and it has been great especially as you can leave it attached due to the lock. To mount to my bike I used the TT bracket as below as their motorcycle GPS brackets only come with clamps to fit small diameter bars (6 or 8mm IIRC).
or you could try
The rubber dampers are good but you do get less choice of where to mount it. If you are feeling rich you could have the TT bracket AND a RAM mount!